Acquired and congenital defects of the heart are now routinely repaired through surgery in cardiac centres in North America. Such repair has become possible because of the development of a technique termed cardioplegia. Cardioplegia refers to the arresting of the heart by the infusion of a chemical solution into the heart by way of the ascending thoracic aorta. The most commonly used cardioplegic solution is a crystalloid solution of high potassium concentration and which solution is maintained at a temperature of 4.degree.-8.degree. C. The infusion of the solution induces a rapid cardiac arrest. The cardiac arrest is essential as it provides a quiet and bloodless operating field for the surgeon and prevents the utilization of high energy phosphate stores by preventing useless electromechanical work. The cold cardioplegic solution also lowers myocardial temperature which is desirable. The cessation of electromechanical activity and the reduction of myocardial temperature reduce the risk of myocardial injury during the performance of cardiac surgery.
Temperature monitoring and multiple dose cardioplegia are now widely used to maintain an electromechanical arrest and to prevent rewarming. Despite this, myocardial injury is still observed following electrocardiac arrest.